Gold is a precious metal that has been valued by people since ancient times.

Gold is a very soft metal when it is pure (24 Kt. is pure gold). It is usually alloyed (mixed with other metals, often silver and copper) to make it harder, but less expensive.

The scientific abbreviation of gold is Au.
The purity of gold jewelry is measured in karats. Some countries hallmark gold with a three-digit number that indicates the parts per thousand of gold. In this system, "750" means 750/1000 gold (equal to 18K); "500" means 500/1000 gold (equal to 12K).